In mammals, injury triggers an organized complex cascade of cellular and biochemical events that result in a healed wound. Wound healing is a complex dynamic process that results in the restoration of anatomic continuity and function; an ideally healed wound is one that has returned to normal anatomic structure, function and appearance.
Chronically contaminated wounds all contain a tissue bacterial flora. These bacteria may be indigenous to the patient or might be exogenous to the wound. Closure, or eventual healing of the wound is often based on a physician7s ability to control the level of this bacterial flora. Infection of wounds by bacteria delays the healing process, since bacteria compete for nutrients and oxygen with macrophages and fibroblasts, whose activity are essential for the healing of the wound. Infection results when bacteria achieve dominance over the systemic and local factors of host resistance. Infection is therefore a manifestation of a disturbed host/bacteria equilibrium in favour of the invading bacteria. This elicits a systemic septic response, and also inhibits the multiple processes involved in wound healing. Lastly, infection can result in a prolonged inflammatory phase and thus slow healing, or may cause further necrosis of the wound. The granulation phase of the healing process will begin only after the infection has subsided.
In clinical practice, a diagnosis of infection is based on the presence of local pain, heat, swelling, discharge and redness, although many clinical indicators, such as inflammation and discharge, have a low predictive value of infection in wounds. Definitive diagnosis is achieved by microbiological analysis of wound samples. Tissue biopsy provides the most accurate results, but this is an invasive procedure that is difficult to achieve for the mass of specimens required. Wound swabbing is the most common wound sampling method used in the UK although its clinical value has been questioned. Furthermore, microbiological diagnosis of wound infection can take 48 to 72 hours, which allows time for infection to further develop if first-line/best-guess treatment is not employed immediately.
There therefore remains a need in the art for a method for the early diagnosis and prognosis of wound infection, and for devices and wound dressings for use in carrying out such methods.
cPLA2 are enzymes that hydrolyse the sn-2 position of membrane glycerophospholipids to liberate arachidonic acid. The activity of these enzymes is therefore important in the production of eicosanoids (e.g. prostaglandins and leukoriennes) and therefore associated with inflammation and host defence mechanisms. A detailed review can be found in Kudo and Murakami, Prostaglandins and other Lipid Mediators (2002) 68-69, 3-58.
There are essentially two groups of PLA2: high molecular weight PLA2 (cytosolic PLA2) and low molecular weight PLA2 (soluble PLA2). High Mol. Wt. cytosolic cPLA2 is normally located intracellularly and as such would not be expected to be present in wound fluid. There are three isoforms of this cPLA2:α (110 kda), β (85 kDa) and γ (60 kDa) (See Kudo and Murakami, 2002). The low molecular weight soluble PLA2's (sPLA2) are known to act intracellularly and, in contrast to cPLA2, we have not found any evidence that the low molecular weight form (sPLA2) is elevated in infected wound fluid.
WO03/101487 describes a method of assessing neural inflammatory disease in an animal by determining the level of phospholipase A2 protein (including cPLA2) in tissue or body fluid such as blood, plasma and cerebrospinal fluid. It does not appear to teach or suggest the association of cPLA2 with extracellular wound fluid or as a marker of bacterial infection.
WO00/54052 describes an assay for detecting cPLA2 in or on red blood cells, in particular for the diagnosis of diseases in which dysfunction of cell signalling systems involving highly unsaturated fatty acids are implicated. This reference does not appear to teach or suggest the testing of extracellular fluid for the presence of cPLA2 to diagnose infection of a wound.
Funakoshi et al. in Pancreas (1991) vol. 6(5), pp 588-594 disclose that serum PLA2 levels are elevated in the sera of patients with pancreatic diseases and that the measurement of serum PLA2 is useful for diagnosis and monitoring of pancreatitis. There is no teaching or suggestion any association of cPLA2 with extracellular wound fluid or as a marker of bacterial infection.